Notes

when that fell arrest i.e. death. Fell means 'cruel, deadly'. 'Arrest' can mean just 'pause or cessation'. The lack of bail referred to in l.2 would have activated the modern sense 'to apprehend someone' (OED 8), as in Hamlet 5.2.288–9: 'this fell sergeant Death | Is strict in his arrest'.

3 some interest some right of ownership or title (OED 1a), rather than 'money paid for the use of money lent' (OED 10a), The conceit here is that the poet's life has a continuing share in the poems; as the poems pass on after the poet's death to the friend, he retains a partial share of the poet through the poems.

5 review 'To survey; to take a survey of' (OED 5a). Manuscript poems in the period were often copied into miscellanies and 'improved' by the copyist. This activates the sense 'To look over or through (a book, etc.) in order to correct or improve; to revise' (OED 3a), as in Holland's translation of Plutarch's Moralia 1274: 'Dionysius had put into his hands a tragedy of his own making, commanding him to review and correct
the same'. This would allay the unease of G. B. Evans, who finds the repetition of review 'rhetorically flat' and suggests emending to renew.

8 spirit monosyllabic. It may mean 'soul' (OED 2a), but its opposition to dregs suggests that it may also mean 'the sweet volatile essence' (as in OED 21a, just becoming active in this period), with perhaps a glance back to the idea of preserving life through the extraction of perfume in 5 and 6.

9 So then (a) when I die; (b) therefore. The past tense (hast lost) suddenly verifies the argument: the poet presents himself as already dead while he offers his consolation to the friend, which rings out like an echo from the grave.

9–11 dregs … knife The four noun clauses in apposition here all describe my body being dead, which is both the useless remnant of life (dregs), a thing that is preyed upon by worms, and something which is conquered in a cowardly manner by a person of no account (the coward conquest of a wretch's knife). The last phrase is problematic because coward functions chiefly as an adjective which is transferred from the wretch to his action, but is also used to register contempt for the weakness of the body (a mere coward). Editors have also fruitlessly speculated as to who the wretch is (Shakespeare, Marlowe, Death, Time, or an unnamed assassin are the favoured candidates). It seems most likely to be a generic term for 'any worthless
person'.